If he doesn’t have many anti air, then a strong air force is the best tool you have.

Once he adds significant AA to his SP Artillery groups you will have to rush at them with light tanks or maybe medium tanks. You need speed in order to close the distance and engage before he gets very many shots off. Cities of course will require mech or moto infantry to conquer in this lightning advance

War is a game that is played with a smile. If you can't smile, grin. If you can't grin keep out of the way til you can. - Winston Churchill

Once he adds significant AA to his SP Artillery groups you will have to rush at them with light tanks or maybe medium tanks. You need speed in order to close the distance and engage before he gets very many shots off. Cities of course will require mech or moto infantry to conquer in this lightning advance

but you get a -50% speed penalty in enemy terrain so this is pretty much suiciding if he's active

his artillery destroy the naval units as some naval units are weaker than artillery

Agree. In this game, destroyers are one of those units weaker than artillery. And as I said before: 'if he's near one of your capital ships (e.g. battleship or cruiser) just expose him to some naval bombardment' ...